Modern design practices require that the loads borne by typical taxis, passenger cars, buses, vans and trucks be supported by a chassis or frame disposed beneath the load to provide structure for the vehicle; the walls, roof, and doors of the vehicle are held in relatively rigid relation to one another by attachment to the chassis. The chassis itself must be suspended over wheels, with the effect that the floor level of such vehicles must be placed at such a height that passengers typically require steps to enter and exit such vehicles, and cargo must be lifted by means of fork trucks, manpower or loading platforms. Loading and discharge of passengers and cargo under these circumstances are necessarily cumbersome and may generate traffic delays in the loading and discharge areas. People with disabilities, wheelchairs, baby-strollers and suitcases cannot easily enter and exit traditional vehicles, and typically require considerable assistance.
To help facilitate loading and discharge of passengers or cargo, there have been developed and placed in use a variety of devices providing special lifting platforms for wheelchairs, pallets, and the like; such devices are typically placed on the side or the rear of buses or vans. These devices, however, are slow and dangerous and do not generally allow for loading or unloading of more than a single person or cargo item at a time.
A related problem in vehicle design is the path of cargo and passengers between the interior of the vehicle and its doors. The path is typically somewhat tortuous, and cargo being loaded, for example, must be funneled through relatively narrow doors dictated by vehicle geometry and thereafter redistributed into the interior of the vehicle.